Metal component absorption enhancer in plant

ABSTRACT

A metal component absorption enhancer which enhances the absorption of at least one metal component selected from the elements belonging to groups 2 to 12 in the third to fourth periods when a plant grows. The metal component absorption enhancer contains 5-aminolevulinic acid or a derivative thereof represented by the following general formula (1), or a salt thereof as an active ingredient:
 
R 2 R 1 NCH 2 COCH 2 CH 2 COR 3   (1)
 
     wherein R 1  and R 2  each independently represents a hydrogen atom, an alkyl group, an acyl group, an alkoxycarbonyl group, an aryl group, or an aralkyl group; R 3  represents a hydroxyl group, an alkoxy group, an acyloxy group, an alkoxycarbonyloxy group, an aryloxy group, an aralkyloxy group, or an amino group, and is used for performing a treatment with 0.001 to 20 ppm of the 5-aminolevulinic acid, the derivative thereof, or the salt thereof per each time.

TECHNICAL FIELD

The present invention relates to a metal component absorption enhancerwhich enhances the absorption of at least one metal component selectedfrom the elements belonging to the groups 2 to 12 in the third to fourthperiods when a plant grows.

BACKGROUND ART

Among essential elements for growth of a plant, carbon, hydrogen, andoxygen are supplied from the air and water. Moreover, three elements ofnitrogen, phosphorus, and potassium are absorbed from soil. However,since the existence thereof in soil is relatively small as compared withthe amount to be absorbed by a plant, they tend to be depleted andeffects easily appear when they are externally supplied, so that theyare called as three elements of fertilizer. For plants, other than thethree elements of fertilizer, there are further essential elements,which specifically include magnesium, sulfur, and calcium classifiedinto major elements and manganese, boron, iron, zinc, copper,molybdenum, chlorine, and nickel classified into minor elements.Moreover, also in human being, deficiency diseases have been known foriron, zinc, copper, manganese, and vanadium. In particular, iron isdepleted in an extremely wide distribution as it is said that one thirdof women suffer from potential iron-deficiency anemia.

Iron (Fe) is involved in the activation of an enzyme as a divalent ironion (Fe²⁺). Moreover, iron enters into a porphyrin ring to betransformed into heme and heme is present at active centers of variousenzymes. Heme iron-containing proteins include cytochromes, peroxidases,and catalases, and iron-sulfur proteins include ferredoxins, which areinvolved in mainly oxidation-reduction reactions and electron transferreactions. Chlorophyll is a substance wherein magnesium ion enters in aporphyrin ring. With regard to a protoporphyrinogen synthetic enzyme anda protochlorophyllide synthetic enzyme as precursor substances of theporphyrin ring synthesis, iron is considered to be involved in thecontrol at a gene level. Therefore, when iron is deficient, thesynthesis of porphyrin is inhibited and chlorophyll is not synthesized,so that a plant exhibits chlorosis, cannot perform photosynthesis, andfinally is blighted.

Copper forms a constitutional component of tissues or a part of enzymesinvolved in metabolisms in a plant body. Common symptoms of itsdeficiency include chlorosis, necrosis, curly leaves, and the like.Plants exhibiting copper deficiency in farm fields include cultivatedplants such as barley, wheat, alfalfa, lettuce, carrot, onion, tomato,tobacco, and citrus.

Manganese has physiological actions such as photosynthesis, respiration,and activation of oxygen and, in many plants, respiration increases asthe amount of manganese increases in the plant bodies. When manganese isdeficient, chlorosis is observed on leaves.

With regard to zinc, a large number of zinc enzymes and the like havebeen found and many in vivo reactions involving zinc are also known. Assymptoms of its deficiency, suppression of elongation growth, inhibitionof protein synthesis, and the like are observed at various sites of avariety of plants.

On the other hand, also in human being, importance of mineral intake hasbeen perceived. According to Nihonjin no Shokuji Sesshu Kijun (DietaryIntake Standard of the Japanese) (Non-Patent Document 1), for example, anew index “desired amount” is set for calcium as a nutrient to beincreased and also estimated average necessary amounts and recommendedamounts are determined for other minerals. Moreover, osteoporosis hasbeen hitherto pointed out owing to deficient intake of calcium but ithas been found that only ingestion of calcium is not a sufficientcountermeasure and magnesium and the like are also necessary.

However, at present, the intake of magnesium and calcium is about 100 mglower than the recommended amount in Dietary Intake Standard of theJapanese. Moreover, in the other minerals, though copper is sufficient,the intake of iron and zinc is lower than the recommended amounts in sexand/or some ages.

As methods for ingesting minerals, there may be mentioned a method foringestion with supplements and a method for ingestion with meals. Ingeneral, minerals have characteristics that the width of zone ofappropriate intake is narrow and a balance between minerals is apt to bedisrupted. The method for ingestion with supplements causes a problemthat overdose disorder owing to excessive ingestion of a specificmineral occurs. Mineral overdose induced by the method for ingestionwith meals is rare other than the case of sodium overdose with sodiumchloride and it is easy to ingest minerals with good balance.Accordingly, as a method for ingesting minerals, it is preferred toingest minerals with meals in just proportion.

Since vegetables abundantly contain various minerals and vitamins,vegetables are main sources of minerals in meals. However, according toShokuryo Jukyu Hyo (Food Supply and Demand Table) (Non-Patent Document2), it is reported that vegetable intake per day has decreased with thechange in dietary habit and only an average of 250 g of vegetables isingested although 350 g thereof per day is required. Thus, in order toincrease mineral intake, it is desired to increase the mineral contentin vegetables.

As a technology for enhancing metal component absorption in a plant, ithas been reported that benzoic acid and/or benzoic acid derivativesenhance absorption of potassium ion (Patent Document 1). Moreover, thereis a report that absorption of calcium ion is enhanced by spraying onthe surface of leaves together with an aqueous amino acid solution(Patent Document 2) but any substance is not known, by which enhancedabsorption of the other metal component(s) is observed.

-   Patent Document 1: JP-A-2002-284607-   Patent Document 2: JP-A-2001-192310-   Non-Patent Document 1: Nihonjin no Eiyo Shoyouryo-Shokuji Sesshu    Kijun-Sakutei Kentoukai, Nihonjin no Shokuji Sesshu Kijun (Dietary    Intake Standard of the Japanese) (2005)-   Non-Patent Document 2: 2004, Ministry of Agriculture, Forestry and    Fisheries, General Food Policy Bureau, March 2006: Shokuryo Jukyu    Hyo (Food Supply and Demand Table)

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

Accordingly, an object of the invention is to provide an absorptionenhancer of at least one metal component selected from the elementsbelonging to the groups 2 to 12 in the third to fourth periods necessaryto a plant.

Means for Solving the Problems

Under such a situation, as a result of extensive studies, the presentinventors have unexpectedly found that 5-aminolevulinic acid, aderivative thereof, or a salt thereof has no effect at a concentrationof 30 ppm or more but exhibits an excellent metal component absorptionenhancing action in the case of a treatment at a low concentration of0.001 to 20 ppm, and thus they have accomplished the invention.

Namely, the invention provide an absorption enhancer of at least onemetal component selected from the elements belonging to the groups 2 to12 in the third to fourth periods in a plant, wherein the absorptionenhancer comprises 5-aminolevulinic acid or a derivative thereofrepresented by the following general formula (1), or a salt thereof asan active ingredient:R²R¹NCH₂COCH₂CH₂COR³  (1)wherein R¹ and R² each independently represents a hydrogen atom, analkyl group, an acyl group, an alkoxycarbonyl group, an aryl group, oran aralkyl group; R³ represents a hydroxyl group, an alkoxy group, anacyloxy group, an alkoxycarbonyloxy group, an aryloxy group, anaralkyloxy group, or an amino group, and the absorption enhancer is usedfor performing a treatment with the 5-aminolevulinic acid, thederivative thereof, or the salt thereof in a concentration of 0.001 to20 ppm per each time.

Also, the invention provides a method for increasing the content of atleast one metal component selected from the elements belonging to thegroups 2 to in the third to fourth periods in a plant, which comprisestreating roots or stems and leaves of a plant or surrounding soil orwater with 5-aminolevulinic acid or a derivative thereof represented bythe following general formula (1), or a salt thereof in a concentrationof 0.001 to 20 ppm per each time:R²R¹NCH₂COCH₂CH₂COR³  (1)wherein R¹ and R² each independently represents a hydrogen atom, analkyl group, an acyl group, an alkoxycarbonyl group, an aryl group, oran aralkyl group; R³ represents a hydroxyl group, an alkoxy group, anacyloxy group, an alkoxycarbonyloxy group, an aryloxy group, anaralkyloxy group, or an amino group.

Advantage of the Invention

The metal component absorption enhancer of the invention can preventmetal deficiency of a plant by enhancing absorption of at least onemetal component selected from the elements belonging to the groups 2 to12 in the third to fourth periods in a plant and also can increasemetal(s), which is ingested by human being from a plant through a meal,by increasing at least one metal component selected from the elementsbelonging to the groups 2 to 12 in the third to fourth periods in aplant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a figure showing a calcium content-enhancing effect in barleyby the action of 5-aminolevulinic acid hydrochloride (shown as ALA inthe figure, the same shall apply hereinafter).

FIG. 2 is a figure showing a manganese content-enhancing effect inbarley by the action of 5-aminolevulinic acid hydrochloride.

FIG. 3 is a figure showing an iron content-enhancing effect in barley bythe action of 5-aminolevulinic acid hydrochloride.

FIG. 4 is a figure showing a copper content-enhancing effect in barleyby the action of 5-aminolevulinic acid hydrochloride.

FIG. 5 is a figure showing zinc content-enhancing effect in barley bythe action of 5-aminolevulinic acid hydrochloride.

FIG. 6 is a figure showing a magnesium content-enhancing effect inbarley by the action of 5-aminolevulinic acid hydrochloride.

FIG. 7 is a figure showing a manganese content-enhancing effect inradish by the action of 5-aminolevulinic acid hydrochloride.

FIG. 8 is a figure showing a zinc content-enhancing effect in radish bythe action of 5-aminolevulinic acid hydrochloride.

FIG. 9 is a figure showing an iron content-enhancing effect in potato bythe action of 5-aminolevulinic acid hydrochloride.

FIG. 10 is a figure showing magnesium content-enhancing effect in potatoby the action of 5-aminolevulinic acid hydrochloride.

BEST MODE FOR CARRYING OUT THE INVENTION

The active ingredient of the metal component absorption enhancer of theinvention is 5-aminolevulinic acid, a derivative thereof (the abovegeneral formula (1)), or a salt thereof.

The alkyl group represented by R¹ and R² in the general formula (1) ispreferably a linear or branched alkyl group having 1 to 24 carbon atoms,more preferably an alkyl group having 1 to 18 carbon atoms, andparticularly, an alkyl group having 1 to 6 carbon atoms is preferred. Asthe alkyl group having 1 to 6 carbon atoms, there may be mentioned amethyl group, an ethyl group, an n-propyl group, an isopropyl group, ann-butyl group, a sec-butyl group, and the like. As the acyl group, alinear or branched alkanoyl group having 1 to 12 carbon atoms, analkenylcarbonyl group, or an aroyl group is preferred, and particularly,an alkanoyl group having 1 to 6 carbon atoms is preferred. As the acylgroup, there may be mentioned a formyl group, an acetyl group, apropionyl group, a butyryl group, and the like. As the alkoxycarbonylgroup, an alkoxycarbonyl group having 2 to 13 carbon atoms in total ispreferred, and particularly, an alkoxycarbonyl group having 2 to 7carbon atoms is preferred. As the alkoxycarbonyl group, there may bementioned a methoxycarbonyl group, an ethoxycarbonyl group, ann-propoxycarbonyl group, an isopropoxycarbonyl group, and the like. Asthe aryl group, an aryl group having 6 to 16 carbon atoms is preferredand there may be, for example, mentioned a phenyl group, a naphthylgroup, and the like. As the aralkyl group, a group composed of an arylgroup having 6 to 16 carbon atoms and the above alkyl group having 1 to6 carbon atoms is preferred and there may be, for example, mentioned abenzyl group and the like.

The alkoxy group represented by R³ is preferably a linear or branchedalkoxy group having 1 to 24 carbon atoms, more preferably an alkoxygroup having 1 to 16 carbon atoms, and particularly, an alkoxy grouphaving 1 to 12 carbon atoms is preferred. As the alkoxy group, there maybe mentioned a methoxy group, an ethoxy group, an n-propoxy group, anisopropoxy group, an n-butoxy group, a pentyloxy group, a hexyloxygroup, an octyloxy group, a decyloxy group, a dodecyloxy group, and thelike. As the acyloxy group, a linear or branched alkanoyloxy grouphaving 1 to 12 carbon atoms is preferred, and particularly, analkanoyloxy group having 1 to 6 carbon atoms is preferred. As theacyloxy group, there may be mentioned an acetoxy group, a propionyloxygroup, a butyryloxy group, and the like. As the alkoxycarbonyloxy group,an alkoxycarbonyloxy group having 2 to 13 carbon atoms in total ispreferred, and particularly, an alkoxycarbonyloxy group having 2 to 7carbon atoms in total is preferred. As the alkoxycarbonyloxy group,there may be mentioned a methoxycarbonyloxy group, an ethoxycarbonyloxygroup, an n-propoxycarbonyloxy group, an isopropoxycarbonyloxy group,and the like. As the aryloxy group, an aryloxy group having 6 to 16carbon atoms is preferred, and there may be, for example, mentioned aphenoxy group, a naphthyloxy group, and the like. As the aralkyloxygroup, one having the above aralkyl group is preferred, and there maybe, for example, mentioned a benzyloxy group and the like.

As R¹ and R² in the general formula (1), a hydrogen atom is preferred.As R³, a hydroxyl group, an alkoxy group, or an aralkyloxy group ispreferred, and more preferably, a hydroxyl group or an alkoxy grouphaving 1 to 12 carbon atoms and particularly, a methoxy group or ahexyloxy group is preferred.

As the derivative of 5-aminolevulinic acid, there may be mentioned5-aminolevulinic acid methyl ester, 5-aminolevulinic acid ethyl ester,5-aminolevulinic acid propyl ester, 5-aminolevulinic acid butyl ester,5-aminolevulinic acid pentyl ester, 5-aminolevulinic acid hexyl ester,and the like. Particularly, 5-aminolevulinic acid methyl ester or5-aminolevulinic acid hexyl ester is preferred.

As the salt of 5-aminolevulinic acid or the derivative thereof, theremay be, for example, mentioned acid addition salts such ashydrochlorides, phosphates, nitrates, sulfates, acetates, propionates,butyrates, valerates, citrates, fumarates, maleates, and malates; andmetal salts such as sodium salts, potassium salts, and calcium salts.These salts are used as aqueous solutions at their use and their actionis the same as in the case of 5-aminolevulinic acid. Any of5-aminolevulinic acid and salts thereof may be used singly or two ormore thereof may be used in combination.

5-Aminolevulinic acid, the derivative thereof, or the salt thereof is aknown compound and can be produced by any method of chemical synthesis,production by a microorganism, and production by an enzyme. A producttherefrom can be used as it is without separation and purificationunless it contains harmful substance(s). In the case where it containsharmful substance(s), it can be used after the harmful substance(s) issuitably removed to a level where no harmful action is observed.

The plants to be targeted for application of the metal componentabsorption enhancer of the invention are not particularly limited andthere may be mentioned plants widely cultivated in agricultural fields.Examples thereof include cereals such as rice, barley, wheat, Japanesebarnyard millet, maize, and foxtail millet; vegetables such as pumpkin,turnip, cabbage, daikon radish, Chinese cabbage, spinach, komatsuna(Brassica rapa var. peruviridis), honewort, asparagus, broccoli, chive,celery, lettuce, garland chrysanthemum, potherb mustard, qing-geng-cai,bell pepper, tomato, eggplant, cucumber, and okra (Abelmoschusesculentus); fruits such as mandarin orange, apple, Japanese persimmon,Japanese apricot, pear, grape, peach, strawberry, water melon, andmelon; flowers such as chrysanthemum, gerbera, pansy, orchid, peonyroot, and tulip; trees such as Rhododendron indicum, sawtooth oak,Japanese cedar (Cryptomeria japonica), Japanese cypress, oak, and beech;beans such as adzuki bean, common bean, soy bean, peanut, broad bean,and garden pea; turf grasses such as Zoysia matrella, bent grass, andJapanese lawn grass; potatoes such as potato, sweet potato, aroid, yam,and taro; scallions such as scallion, Wakegi green onion, onion, andRakkyo (Allium chinense); pasture grasses such as alfalfa, clover, andChinese milk vetch; and root vegetables such as carrot, daikon radish,radish, turnip, and edible burdock. Cereals, vegetables, rootvegetables, and potatoes are preferred, and spinach, barley, radish, andpotato are more preferred.

In the invention, as the elements belonging to the groups 2 to 12 in thethird to fourth periods, there may be mentioned magnesium, calcium,vanadium, manganese, iron, copper and zinc, and germanium, and preferredare magnesium, calcium, manganese, iron, copper, and zinc. Particularly,the absorption enhancer of the invention is suitably used for enhancingiron absorption.

In the invention, as the metal component absorption enhancer,5-aminolevulinic acid, a derivative thereof, or a salt thereof alone maybe used but, in addition thereto, a plant growth regulator, a sugar, anamino acid, an organic acid, an alcohol, a vitamin, a mineral, and/orthe like can be mixed. As the plant growth regulator to be used herein,there may be, for example, mentioned brassinolides such asepibrassinolide, choline agents such as choline chloride and cholinenitrate, indolebutyric acid, indoleacetic acid, ethychlozate agent,1-naphthylacetamide agent, isoprothiolane agent, nicotinic acid amideagent, hydroxyisoxazole agent, calcium peroxide agent, benzylaminopurineagent, methasulfocarb agent, oxyethylene docosanol agent, ethephonagent, chlochinphonac agent, gibberellin, streptomycin agent, daminozideagent, benzylaminopurine agent, 4-chlorophenoxyacetic acid (4-CPA)agent, ancymidol agent, inabenfide agent, uniconazole agent, chlormequatagent, dikeblack agent, mefluidide agent, calcium carbonate agent,piperonyl butoxide agent, and the like.

As the sugar, there may be, for example, mentioned glucose, sucrose,xylitol, sorbitol, galactose, xylose, mannose, arabinose, madurose,sucrose, ribose, rhamnose, fructose, maltose, lactose, maltotriose, andthe like.

As the amino acid, there may be, for example, mentioned asparagine,glutamine, histidine, tyrosine, glycine, arginine, alanine, tryptophan,methionine, valine, proline, leucine, lysine, isoleucine, and the like.

As the organic acid, there may be, for example, mentioned formic acid,acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid,phthalic acid, benzoic acid, lactic acid, citric acid, tartaric acid,malonic acid, malic acid, succinic acid, glycolic acid, glutamic acid,aspartic acid, maleic acid, caproic acid, caprylic acid, myristic acid,stearic acid, palmitic acid, pyruvic acid, α-ketoglutaric acid,levulinic acid, and the like.

As the alcohol, there may be, for example, mentioned methanol, ethanol,propanol, butanol, pentanol, hexanol, glycerol, and the like.

As the vitamin, there may be, for example, mentioned nicotinic acidamide, vitamin B₆, vitamin B₁₂, vitamin B₅, vitamin C, vitamin B₁₃,vitamin B₁, vitamin B₃, vitamin B₂, vitamin K₃, vitamin A, vitamin D₂,vitamin D₃, vitamin K₁, α-tocopherol, β-tocopherol, γ-tocopherol,σ-tocopherol, p-hydroxybenzoic acid, biotin, folic acid, nicotinic acid,pantothenic acid, α-lipoic acid, and the like.

As the mineral, there may be, for example, mentioned nitrogen,phosphorus, potassium, calcium, boron, manganese, magnesium, zinc,copper, iron, molybdenum, magnesium, and the like.

The metal component absorption enhancer of the invention contains5-aminolevulinic acid, a derivative thereof, or a salt thereof and thetreatment concentration per each time is 0.001 to 20 ppm as the5-aminolevulinic acid, the derivative thereof, or the salt thereof. Inthe case where the treatment concentration is less than 0.001 ppm and inthe case where the concentration is more than 20 ppm, the metalcomponent absorption effect is not sufficient in both cases.Particularly preferred treatment concentration is 0.01 to 10 ppm.

The metal component absorption enhancer of the invention is used throughthe treatment of roots or stems and leaves of a plant or surroundingsoil or water. Specifically, the enhancer may be used for foliagetreatment (a foliage-treating agent) or may be used for soil treatment(a soil-treating agent). Moreover, the enhancer may be absorbed before aplant is planted or a cutting is planted. Furthermore, the enhancer maybe added into water at hydroponics.

In the case where the enhancer is used as a foliage-treating agent, itis preferred that 5-aminolevulinic acid, a derivative thereof, or a saltthereof is incorporated in a concentration of preferably 0.001 to 20ppm, more preferably 0.01 to 10 ppm, particularly preferably 0.1 to 5ppm, further preferably 0.2 to 1.5 ppm and is used in a ratio of 10 to1000 L, particularly 50 to 300 L per 10 are. The kind and amount of thespreading agent to be used for a plant such as monocotyledon to whichthe foliage-treating agent is hardly attached to its leave surfaces arenot particularly limited.

In the case where the enhancer is used as a soil-treating agent, it ispreferred to use 5-aminolevulinic acid, a derivative thereof, or a saltthereof in a ratio of preferably 0.1 to 20000 mg, more particularly 10to 10000 mg, particularly preferably 100 to 5000 mg, further preferably200 to 1500 mg per 10 are. As concentration, preferred is 0.001 to 20ppm, more preferred is 0.01 to 10 ppm, particularly preferred is 0.1 to5 ppm, and further preferred is 0.2 to 1.5 ppm. It is preferred to usethe agent having a concentration of the above range in an amount of 10to 1000 L per 10 are.

In the case where 5-aminolevulinic acid, a derivative thereof, or a saltthereof is added to a water culture medium, it is desired that theconcentration of the 5-aminolevulinic acid, the derivative thereof, orthe salt thereof is preferably 0.001 to 20 ppm, more preferably 0.01 to10 ppm, particularly preferably 0.05 to 5 ppm, further preferably 0.1 to3 ppm

EXAMPLES

The following will specifically describe the invention with reference toExamples but they are cited only for illustration and do not limited theinvention.

Example 1 Calcium Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Two containers were provided and soil was placed in each of them, inwhich seeds of spinach were uniformly planted. From the day when theseeds were planted, water was applied once a day by means of asprinkling can. To one of the container, tap water in which5-aminolevulinic acid hydrochloride was dissolved in a concentration of1 ppm was sprayed once a day in an amount of about 50 mL by means of asprayer. Thinning was performed 3 weeks after the seed planting, andharvest was performed on the two containers after 38 days. At theharvest, the upper portions from the ground were cut out and the plantbodies were subjected to natural drying. After drying, the plant bodieswas ground one by one in a mortar, the calcium content in dry weight wasmeasured by ICP, and the concentration was calculated. Table 1 showsaverage values of calcium concentration for the case where5-aminolevulinic acid was added and for the case where it was not added.

TABLE 1 Average value of calcium concentration in spinach (%)Administration of 5- No 5-aminolevulinic acid aminolevulinic acid (n =18) (n = 22) 0.68 0.61

As shown in Table 1, a calcium content-enhancing effect was observed inspinach by the spraying of 5-aminolevulinic acid hydrochloride and thusit was fond that the compound is useful as a metal component absorbent.

Example 2 Manganese Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 1 and the manganeseconcentration in spinach was calculated. The results are shown in Table2.

TABLE 2 Average value of manganese concentration in spinach (%)Administration of 5- No 5-aminolevulinic acid aminolevulinic acid (n =18) (n = 22) 0.031 0.027

As shown in Table 2, a manganese content-enhancing effect was observedin spinach by the spraying of 5-aminolevulinic acid hydrochloride andthus it was fond that the compound is useful as a metal componentabsorbent.

Example 3 Iron Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 1 and the ironconcentration in spinach was calculated. The results are shown in Table3.

TABLE 3 Average value of iron concentration in spinach (%)Administration of 5- No 5-aminolevulinic acid aminolevulinic acid (n =18) (n = 22) 0.049 0.015

As shown in Table 3, an iron content-enhancing effect was observed inspinach by the spraying of 5-aminolevulinic acid hydrochloride and thusit was fond that the compound is useful as a metal component absorbent.

Example 4 Copper Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 1 and the copperconcentration in spinach was calculated. The results are shown in Table4.

TABLE 4 Average value of copper concentration in spinach (%)Administration of 5- No 5-aminolevulinic acid aminolevulinic acid (n =18) (n = 22) 0.029 0.023

As shown in Table 4, a copper content-enhancing effect was observed inspinach by the spraying of 5-aminolevulinic acid hydrochloride and thusit was fond that the compound is useful as a metal component absorbent.

Example 5 Zinc Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 1 and the zincconcentration in spinach was calculated. The results are shown in Table5.

TABLE 5 Average value of zinc concentration in spinach (%)Administration of 5- No 5-aminolevulinic acid aminolevulinic acid (n =18) (n = 22) 0.048 0.033

As shown in Table 5, a zinc content-enhancing effect was observed inspinach by the spraying of 5-aminolevulinic acid hydrochloride and thusit was fond that the compound is useful as a metal component absorbent.

Example 6 Calcium Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Barley (race: Fiber snow) was seeded on river sand, sprouted, and grownfor 9 days. After the growth, the sand was washed out with caring so asnot to hurt roots and the roots were cut so as to adjust the length to 2cm. The roots were immersed in a water culture medium A and hydroponicswas performed. Table 6 shows the composition of the water culture mediumA.

As water culture media, one in which no 5-aminolevulinic acid wasdissolved and those in which the compound was dissolved so that each onehas a concentration of 0.1, 0.3, or 1 ppm were prepared. The waterculture medium was replaced 13 days after the start of the hydroponics,and hydroponics was continued for another 6 days. After the hydroponics,the plant was dried at 50° C. for two nights and then was subjected toICP metal analysis. The results are shown in FIG. 1.

TABLE 6 Used salt g/L NH₄NO₃ 0.028575 NaNO₃ 0.0425 NaH₂PO₄•2H₂O 0.0126K₂SO₄ 0.04345 CaCl₂•2H₂O 0.073375 MgSO₄•7H₂O 0.12165 DTPA-Fe 0.002488MnSO₄•5H₂O 0.0011 H₂BO₃ 0.000713 ZnSO₄•7H₂O 0.000225 CuSO₄•5H₂O 8.75E⁻⁰⁶(NH₄) 6Mo₇O₂₄•4H₂O 2.25E⁻⁰⁶

As shown in FIG. 1, a calcium content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 7 Manganese Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0, 0.3,or 1 ppm and the manganese concentration in barley was analyzed. Theresults are shown in FIG. 2.

As shown in FIG. 2, a manganese content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 8 Iron Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that thecomposition of the water culture medium was changed to twofoldconcentration of the water culture medium A and the concentration of theadded 5-aminolevulinic acid was adjusted to 0, 1, or 3 ppm, and then theiron concentration in barley was analyzed. The results are shown in FIG.3.

As shown in FIG. 3, an iron content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 9 Copper Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that the waterculture medium A and a water culture medium having a composition whichwas twice the composition of the water culture medium A were used andthe concentration of the added 5-aminolevulinic acid was adjusted to 0,0.1, or 0.3 ppm, and then the copper concentration in barley wasanalyzed. The results are shown in FIG. 4 (left one in the figure is forthe water culture medium A and right one is for twofold concentration ofthe water culture medium A).

As shown in FIG. 4, a copper content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 10 Zinc Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0, 0.1,or 0.3 ppm, and the zinc concentration in barley was analyzed. Theresults are shown in FIG. 5.

As shown in FIG. 5, a zinc content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 11 Magnesium Absorption-Enhancing Effect of 5-AminolevulinicAcid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0, 0.1,0.3, 1, or 3 ppm, and the manganese concentration in barley wasanalyzed. The results are shown in FIG. 6.

As shown in FIG. 6, a magnesium content-enhancing effect was observed inbarley by the addition of 5-aminolevulinic acid hydrochloride to thewater culture medium and thus it was fond that the compound is useful asa metal component absorbent.

Example 12 Manganese Absorption-Enhancing Effect of 5-AminolevulinicAcid

Radish was sowed in a pot of 1/57000×10 are in an amount of 6 seeds perpot and grown. An andosol (Kuroboku-soil) was used as soil and wateringwas suitably performed. On 11th day after the seeding (a two trueleaves-developed stage), a solution containing 5-aminolevulinic acidhydrochloride prepared to a concentration of 0, 1, or 10 ppm in adeveloping agent-diluted (2000 times) liquid was applied to foliagetreatment. Moreover, on this occasion, DTPA iron and magnesium sulfatewere transformed into solutions having a concentration of 1.8 and 4.5ppm in terms of Fe and MgO, respectively, and were applied to foliagetreatment together with 5-aminolevulinic acid hydrochloride. The amountused for the treatment was 100 L per 10 are. The number of pots was 5pots per test plot. On 15th day and 20th day after the seeding, thinningwas performed and the number of plants per pot was adjusted to 4individuals. On 25th day after the seeding, the plants were harvestedand completely dried at 50° C. for two nights. Thereafter, they arepulverized and mixed in a mixer and then IPC metal analysis wasperformed. The results are shown in FIG. 7.

As shown in FIG. 7, a manganese content-enhancing effect was observed inradish by the application of 5-aminolevulinic acid hydrochloride to thefoliage treatment and thus it was fond that the compound is useful as ametal component absorbent.

Example 13 Zinc Absorption-Enhancing Effect of 5-Aminolevulinic Acid

Similar operations were performed as in Example 12 and the zincconcentration in radish was analyzed. The results are shown in FIG. 8.

As shown in FIG. 8, a zinc content-enhancing effect was observed inradish by the application of 5-aminolevulinic acid hydrochloride to thefoliage treatment and thus it was fond that the compound is useful as ametal component absorbent.

Example 14 Iron Absorption-Enhancing Effect of 5-Aminolevulinic Acid

A seed tuber of potato was subjected to light-exposure and sprout-growthto stimulate germination. The germinated potato was planted in a pot of1/20000×10 are in an amount of 1 tuber per pot. On 30th day after theplanting (height of terrestrial portion: about 30 cm), 5-AminolevulinicAcid hydrochloride was dissolved in a developing agent-diluted (2000times) liquid in a concentration of 0 or 1 ppm and was applied tofoliage treatment. Thereafter, the foliage treatment was performed 8times every other week. The number of pots was 3 pots per test plot andnew sprouts were removed while a strong thick sprout was left so thatthe number of sprout per pot was 1. On 105th day after the planting,potato as tubers was harvested and the tubers were selected from eachtest plot so that the total weight was 120±10 g. Then, they were paredand completely dried at 50° C. for two nights. Thereafter, they arepulverized and mixed in a mixer and then IPC metal analysis wasperformed. The results are shown in FIG. 9.

As shown in FIG. 9, an iron content-enhancing effect was observed inpotato by the application of 5-aminolevulinic acid hydrochloride to thefoliage treatment and thus it was fond that the compound is useful as ametal component absorbent.

Example 15 Magnesium Absorption-Enhancing Effect of 5-AminolevulinicAcid

Similar operations were performed as in Example 14 and the magnesiumconcentration in potato was analyzed. The results are shown in FIG. 10.

As shown in FIG. 10, a magnesium content-enhancing effect was observedin potato by the application of 5-aminolevulinic acid hydrochloride tothe foliage treatment and thus it was fond that the compound is usefulas a metal component absorbent.

Comparative Example 1 Calcium Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm, and the calcium concentration in barley was analyzed. The resultsare shown in FIG. 1.

As shown in FIG. 1, a calcium content-enhancing effect was not observedin barley in the case where 5-aminolevulinic acid hydrochloride wasadded to the water culture medium in a concentration of 30 ppm.

Comparative Example 2 Manganese Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm, and the manganese concentration in barley was analyzed. The resultsare shown in FIG. 2.

As shown in FIG. 2, a manganese content-enhancing effect was notobserved in barley in the case where 5-aminolevulinic acid hydrochloridewas added to the water culture medium in a concentration of 30 ppm.

Comparative Example 3 Iron Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm and the iron concentration in barley was analyzed. The results areshown in FIG. 3.

As shown in FIG. 3, an iron content-enhancing effect was not observed inbarley in the case where 5-aminolevulinic acid hydrochloride was addedto the water culture medium in a concentration of 30 ppm.

Comparative Example 4 Copper Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm, and the copper concentration in barley was analyzed. The resultsare shown in FIG. 4.

As shown in FIG. 4, a copper content-enhancing effect was not observedin barley in the case where 5-aminolevulinic acid hydrochloride wasadded to the water culture medium in a concentration of 30 ppm.

Comparative Example 5 Zinc Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm, and the zinc concentration in barley was analyzed. The results areshown in FIG. 5.

As shown in FIG. 5, a zinc content-enhancing effect was not observed inbarley in the case where 5-aminolevulinic acid hydrochloride was addedto the water culture medium in a concentration of 30 ppm.

Comparative Example 6 Magnesium Absorption-Enhancing Effect of5-Aminolevulinic Acid

Similar operations were performed as in Example 6 except that theconcentration of the added 5-aminolevulinic acid was adjusted to 0 or 30ppm and the magnesium concentration in barley was analyzed. The resultsare shown in FIG. 6.

As shown in FIG. 6, a magnesium content-enhancing effect was notobserved in barley in the case where 5-aminolevulinic acid hydrochloridewas added to the water culture medium in a concentration of 30 ppm.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

The present application is based on Japanese Patent Application No.2007-189879 filed on Jul. 20, 2007, and the contents are incorporatedherein by reference.

INDUSTRIAL APPLICABILITY

According to the present invention, there can be provided an absorptionenhancer of at least one metal component selected from the elementsbelonging to the groups 2 to 12 in the third to fourth periods necessaryto a plant.

The invention claimed is:
 1. A method for increasing the content of atleast one metal component selected from the group consisting of theelements of manganese, iron, copper and zinc in a plant, which comprisestreating the foliage of a plant with a composition containing5-aminolevulinic acid or a derivative thereof represented by thefollowing general formula (1), or a salt thereof in a concentration of0.2 to 5 ppm per each time:R²R¹NCH₂COCH₂CH₂COR³  (1) wherein R¹ and R² each independentlyrepresents a hydrogen atom, an alkyl group, an acyl group, analkoxycarbonyl group, an aryl group, or an aralkyl group; R³ representsa hydroxyl group, an alkoxy group, an acyloxy group, analkoxycarbonyloxy group, an aryloxy group, an aralkyloxy group, or anamino group, wherein a soil or water culture medium in which the plantgrows contains at least one metal component selected from the groupconsisting of the elements of manganese, iron, copper and zinc, and/orthe composition further contains at least one metal component selectedfrom the group consisting of the elements of manganese, iron, copper andzinc, whereby the content of at least one metal component selected fromthe group consisting of the elements of manganese, iron, copper and zincin the plant is increased.
 2. The method for increasing the content of ametal component according to claim 1, wherein the plant is selected fromthe group consisting of spinach, barley, radish and potato.